Molding composition.



UNITED STATES PATENT OFFICE.

JAMES P. A. MOODY, 0]! WILKINSBURG, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

PatentedAnr. SJQJQ.

MOLDING COMPOSITION.

1,300,218, Specification of Letters Patent. Ho Drawing. Application filed April 12, 1915. Serial No. 20,752.

To all whom it may concern:

Be it known that I, JAMES P. A. McCox, a subject of the King of Great Britain, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Molding Com ositions, of which the followis a speci cation.

invention relates to the manufacture of molded materials and it has special reference to compositions that are adapted for use in the manufacture of molded electrical insulation.

The objects of my invention are to pre are novel, effective and inexpensive materia s of high insulating efficiency and to form such materials into molded articles which shall have superior physical properties.

My novel moldin compositions are prepared from inert llers such as asbestos, wood flour and the like, united into a solid mass by means of certain resinous binders which I have found to be particularly well suited to this urpose.

The binders whlch I resinous roducts of t plrefer to employ are e partial or complete polymerization of certain aromatic carbon compounds, particularly indene, cumaron and their isomers. Both indene and cumaron are produced as such in the fractional distillation of coal tar,

re ared s thetically. Whether prepared by istillation from coal tar or synthetically, they are readily polymerized by means of sulfuric acid, which, when added to a solution of either or both of these substances,

forms a artly polymerized resinous material. In the case of this material is a mixture of paraindene and paracumaron. The partly polymerized re sins are readily solub e in man of the usual organic solvents, includ1ng coa as anthracenc oil.

Paraindene and paracumaron, either separately or mixed in any proportions, are exbinders for the manufacture of elec: trical insulating material,and they are adapted for use both in hot molding and m coldmoldmg processes. Furthermore, the

60 proportions in which they may be nnxed these and they may also be the coal tar distillate,-

tar oils such the final articles ex'c with fillers may be varied to an almost unlimited degree if the treatment to which the moldin mixture is subjected is correspondingly a tered, as will be hereinafter more fully set forth. The partial and complete polymerization products of the isomers of indene and cumaron are likewise suitable for my use, either singly or mixed. If a molded material containing a large amount of filler and a small amount of binder is desired it is sometimes necessary to pre-form the molded articles before the actual molding operation, which should be performed with heat. One satisfactory mold ing mixture for carrying out this modification of my'process is made by mixing about 90% of ground asbestos fibers, about 5% of paramdene', paracumaron or mixtures of bodies, and about 5% of a olymerizable vegetable oil, such as raw ina wood oil; This mixture should be made into a pulp or sludge with a suitable solvent, such as benzol, and pre-formed in the cold in a mold which corresponds in sha e to the finished molded articles desired, ut which is somewhat larger in size. The material is heated in the pie-forming mold at about 60 C. until the solvent is driven 03, after which the pre-formed articles are given the final molding treatment in hot molds, to eflect' the complete polymerization of the resinous binder and of the ve etable oil. If the binder-is added to the'orlginal material in a nonolymerized condition, it may be completely polymerized in the hot mold.

It is particularly desirable to add a small quantity of China wood tures of this character, because thisoll increases in volume on polymerizing, and this increase in volume compensates for the shrinkage caused the expulsion of solvent from the molded articles. Shrinka in the mold may be entirelvohyiated by t e use of suitable amounts of, -China wood oil, and

solid can thereforebe molded directly oil to moldinnmixin. the molded articles. T;h'e "polymerized oil has the further advanta that it renders e dingy tough as well asimproving their dielectric strength.

A very eificient mixture for cold molding is formed by using about 70 parts of asbestos with about 80 parts of the resinous binders described above. It is also advantageous to add a small amount of China wood oil, as in the case of hot molding1 mixtures but much less solvent is used in t e cold moldin operations and, therefore, 1% or 2% 0 China wood oil is suflicient to compensate for the shrinkage in the mold. The filler and the resins may be mixed dry or the meme may be first dissolved in a suitable solvent. If the latter course is followed, a solution of resins is preferably sprayed into the filler and thoroughly mixed with it.

If the resins and the binder are mixed in the dry state, the resins should be finely ground and mixed with the filler, the mixture being then sprayed with a small amount of a solvcat, which is preferably a mixture of aided solvents, that is to say, solvents of di erent boiling oints, in order that the solvent may not su denly vaporize within the molded articles, thereby causing war ing or distor tion of the molded articles, ut may come off gradually, the fractions being volatilized in the order of their boiling points. The solvents, when sprayed in small amounts into the mixture-of binder, and filler, perform the softenin efl'ect set forth in my Patent' No. 1,286,3 0, dated Dec. 3, 1918, and assigned to the Westinghouse Electric and Manufacturing Uompan The mixture prepared in this manner is ry to the touch at is plastic under pressure and ma readily be molded cold in automatic mol ing machines. After being molded, the

7 pieces are heated in an oven at a tem erat re of between 100 C. and 120 for a least six hours. The heat is then raised to about 200 C. and maintained at this point for twenty-four hours longer, when substantially all of the solvent will have been expelled and the resins and the China wood oil will be completely polymerized.

The amount of binder may be increased considerably above 30%, but the molded pieces must be heated longer, in roportion to such increase in the amount 0 binder in order to completely polymerize the bin er.

The resinous binders, which I have described above when derived from coal tar are brown in color, and the color of the finished articles may be varied by addin any desired igment, the color of which wi combine wit the natural brown color of the binder. Lamp black, for example, may be added toreduce dark brown and black articles and ferric oxid may be added to produce dark red,molded articles.

The molded'materials repared in accord ance with the process above are exceedingly tong1 and of high tensile and dielectric strengt They ing be cut, turned and polished in an desi manner, and even the cold mol articles leave the mold with a polish which ordinarily will require no additional] finishing. It is obvious that the specific examples set forth ma be variously modified by persons skilled in the art to which my invention appertains and that many other proportions and filling materials may be employed without departing from the spirit of my invention. It is, therefore, to be understood that m invention comprehends all such modi cations, changes and adaptations as fall within the sco e of the appended claims. claim as my invention:

1. A molding com osition comprisin a filler, a polymerizab e vegetable oil which expands upon polymerization, and a resinous binder that contains at least one of a group of substances including indene, cumaron and their isomers, and the partial polymerization products of the said substances, said binder shrinkin upon polymerization, said oil and saidawinder bein combined in such proportion that sai shrinking effect is substantially neutralized by said expanding effect in the polymerization of said composition.

2. A molding composition comprising a filler, China wood oil and a resinous binder that contains at least' one of a group of substances including, indene, cumaron and their v isomers, and the partial polymerization products of the said substances, said binder shrinking upon polymerization, and said 0'1 and said binder being combined in such proportion that said shrinkingefi'ect is substantially neutralized by the expansive effect of said oil in the polymerization of the composition.

3. A molding composition 3 comprising comminuted asbestos, China wood oil and a resinous binder that contains at least one of a group of substances including indene,

cumaron, paraindene and paracumaronin a partly polymerized conditlon.

4. A molding composition comprising a;

filler, a resinous binder that contains at least one of a group of substances including indene, cumaron and their isomers and the polymerization products of the said substances, and a polymerizable vegetable oil, in unpolymerized state, which expands during polymerization, the latter being in such quantity as to substantially counteract the 6. A molding composition comprising a filler, a polymerizable impregnator therein which expands upon polymerization, and an additional polymerizable impregnator 5 therein which shrinks upon polymerization, said impregnators being present in such relative proportions that said shrinkage is position.

molding oom- In testimony whereof, I have hereunto subscribed my name this 30th day of March,

JAMES P. A. MoCOY. 

